Typical end-of-car rail car cushioning devices of the type suitable for incorporating the present invention are shown in U.S. Pat. No. 3,568,855 to Seay et al; U.S. Pat. No. 3,589,527 to Seay et al; U.S. Pat. No. 4,026,418 to Hawthorn; and U.S. Pat. No. 4,739,889 to Bomgardner.
Such end-of-car cushioning devices may be installed in a new freight car or in a freight car which is brought into a shop and rebuilt.
After the cushioning devices have been installed and the rail car is put into service, the rail car is repeatedly used over a period of many months, or many years, with little or no inspection or maintenance.
The cushioning devices continue to be used until the respective rail car is brought into a shop for overhaul or rebuild, or until a particular cushioning device obviously has failed and becomes inoperative. The cushioning device which has failed is usually rebuilt with all worn or broken parts being replaced with new parts. The resulting rebuilt unit is substantially of the same quality as a new unit.
The new cushioning devices incorporate the improvements which extend the useful service life of the cushioning devices and also improvements which reduce the cost of the cushioning devices.
The older cushioning devices of a particular model, which are returned for overhaul and rebuild, incorporate only the improvements for that particular model where the older devices are suitable to incorporate the improvements. The older devices become obsolete when the older units are no longer suitable for rebuild into devices acceptable for further use.
The improved cylinder head and slider valve apparatus of the present invention is valuable when incorporated into new cushioning apparatus and also when incorporated as replacement components of rebuilt cushioning apparatus.